Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G23/00—Compounds of titanium
  • C01G23/003—Titanates
  • C01G23/005—Alkali titanates
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/36—Compounds of titanium
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/02—Amorphous compounds
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/40—Electric properties
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/60—Optical properties, e.g. expressed in CIELAB-values

Definitions

• the present invention relates to a process for preparing a metamorphosed alkali metal titanate.
• Alkali metal titanates are represented by the formula
• n and m are respectively an integer not more than 10, and are well known as insulating materials having excellent heat resistance and high refractive index.
• n and m are respectively an integer not more than 10, and are well known as insulating materials having excellent heat resistance and high refractive index.
• attempts have been made to modify or metamorphose such alkali metal titanates, in accordance with diversified industrial needs.
• attempts have been with a view to lowering the insulating property of an alkali metal titanate or, in other words, making an alkali metal titanate semiconductive and further conductive, without extinction of its heat resistance and its reinforcing property for composites owing to its shape, or with a view to coloring an alkali metal titanate having in general a large refractive index and high whiteness and being difficult to apply to colored materials, into black, blue, etc.
• the present invention provides a process for preparing metamorphosed alkali metal titanates which comprises heating a mixture of at least one alkali metal compound capable of being decomposed by heating into an oxide of the alkali metal and a gas and titanium dioxide, under a non-oxidative atmosphere, in the presence of at least one carbide represented by the formula
• M is an element except carbon selected from Groups III, IV and V in the Periodic Table, and Z is an integer corresponding to the valency of M.
• the metamorphosed alkali metal titanates obtained according to the process of this invention may take various embodiments depending on the composition of raw materials and the conditions of metamorphosis.
• the process of this invention is free from such danger as involved in conventional hydrogenation processes and does not cause any lowering of heat resistance owing to the remaining carbonous compounds as noticed in the hydrogenated alkali metal titanates obtained by the known processes using a carbonous compound.
• the carbide an essential component of the process of this invention, is also metamorphosed into a conductive one because the resultant metamorphosed alkali metal titanate is provided with conductivity even when it contains said carbide, although the reaction mechanism is also not fully clarified.
• the process according to the present invention is extremely advantageous as a method of providing conductive compounds having excellent heat resistance.
• the metamorphosed alkali metal titanates of the present invention show no lowering in conductivity even when they are in contact with an oxidative atmosphere.
• alkali metal compounds capable of being decomposed by heating into alkali metal oxides and gases according to the process of this invention include carbonates, hydroxides and halogenides of an alkali metal and organo-alkali metal compounds, more particularly sodium carbonate, sodium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate, lithium carbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium chloride, sodium bromide, sodium iodide, sodium fluoride, potassium chloride, potassium bromide, potassium iodide, potassium fluoride, lithium chloride, sodium alcoholate, potassium alcoholate, lithium alcoholate, rubidium hydroxide, cesium hydroxide, etc.
• Alkali metal carbonates among them can be preferably utilized, as they are available at low prices and the non-oxidative atmosphere can be maintained by them easily.
• titanium dioxides Both amorphous and crystalline (anatase type and rutile type) titanium dioxides may be used as the titanium dioxide according to the present invention. Those various forms of titanium dioxide may be properly selected and used in accordance with the conditions of metamorphosis as mentioned below.
• Well known compounds can be widely used as the carbides represented by the formula (I), and they include boron carbide, silicon carbide, titanium carbide, germanium carbide, tin carbide, lead carbide, phosphorus carbide, etc. Preferred among them are silicon carbide, boron carbide, titanium carbide, etc. They may be used either individually or as a mixture of two or more of them.
• titanium dioxides, alkali metal compounds and carbides are not specified in the present invention. However, highly pure ones are preferred when the products are used for electric and electronic applications. Moreover, those of small particle size are preferred in order to carry out the reaction rapidly. As for the carbides, it is preferred that their size is not larger than several ⁇ m.
• the mixing ratio of titanium dioxide and alkali metal compound is not limited specifically and can be selected from a wide range of values. However, it is preferred that they are mixed in such ratio that the numbers of titanium atom to the numbers of alkali metal atom (Ti/Ma) are 1:1 to 10:1, more particularly 1:3 to 8:1.
• the amount of the carbide represented by the formula (I) is also not limited specifically and can be selected from a wide range of values. However, it is preferred to add usually 5 to 100% by weight, more particularly 10 to 40% by weight, of the carbide to the total amount of titanium dioxide and the alkali metal compound.
• the non-oxidative atmosphere in the present invention means a non-oxidative atmosphere containing substantially more than 90% by volume of either one or a mixture of two or more of reducing gases (except hydrogen gas) such as carbon mono-oxide and inert gases such as nitrogen, helium, carbon dioxide, etc. Preferred among them are an atmosphere of nitrogen gas and carbon dioxide gas.
• a mixture of titanium dioxide, alkali metal compound and carbide may be simply charged into a container, deaerated and then heated.
• a compound that decomposes, vaporizes or burns at temperatures below 500° C. hereinafter, such compound is referred to as "void-forming agent" and then heat the admixture, in order to perform the deaeration effectively and make fibrous growth of the alkali metal titanate easy.
• a void-forming agent is added to a mixture of titanium dioxide, alkali metal compound and carbide and the admixture is shaped into a molding, whereby the rate of voids before heating is reduced and migration of air into the molding is excluded as far as possible.
• the molding thus obtained is heated in a non-oxidative medium at a temperature higher than that causes decomposition, vaporization or combustion of the void-forming agent, non-oxidative voids are formed in the molding as a result of decomposition, vaporization or incomplete combustion of the agent and hence the metamorphosed alkali metal titanate of the present invention can be made to grow in fibrous form.
• Such compounds should be exluded that evolve a large amount of oxidative components by heating in a non-oxidative atmosphere.
• Compounds that are liquefied at room temperature or under the conditions of molding operation, and that act as binders when a mixture of titanium dioxide, alkali metal compound and carbide is molded, are more preferable from the viewpoint of the workability in molding.
• Such preferable void-forming agents include, for example, water, ammonia, amino compounds, hydrocarbon compounds, carbohydrate compounds, nitrogen-containing compounds, various synthetic resins, or mixtures of two or more of them.
• water, hydrocarbon compounds, glycerol, ethylene glycol, carbohydrate compounds such as starch, saccharides, etc., nitrogen-containing compounds such as urea and its derivatives, polyvinyl alcohol, and synthetic resins such as butyral resin, polyvinyl acetate resin, atactic polyethylene, liquid polypropylene, polybutene, acrylic resin, etc. are especially preferred.
• the amount of incorporating these void-forming agents may vary without limitation, it is preferred to use the agent in an amount not more than 50% by weight to the total amount of the mixture of titanium dioxide, alkali metal compound and carbide. Too large an amount of void-forming agent is undesirable because excessive energy is required for the decomposition, vaporization or combustion of the void-forming agent, having no direct relation to the reaction, and because the contact between titanium dioxide and alkali metal compound becomes insufficient and the reaction efficiency is decreased.
• any conventional method wherein a uniform mixture prepared by a conventional method and heated at room temperature or at such temperature range that does not cause vaporization or decomposition of the void-forming agent is subjected to any one of the following molding processes:
• the molding obtained has a larger surface area.
• the thicker the molding the larger the temperature gradient therein. It is necessary to control the thickness of moldings in order to avoid unevenness of the heating, i.e., unevenness of the metamorphosis.
• the heat-treatment of the present invention may be performed by heating, under a non-oxidative atmosphere, an intimate mixture or a molding at a temperature higher than that which causes decomposition of the alkali metal compound or void-forming by the void-forming agent to deaerate it and subsequently at a temperature of 900° to 1300° C., preferably at a temperature not higher than 1200° C., still maintaining the non-oxidative atmosphere.
• a method in which a molding consisting of a mixture of titanium dioxide, alkali metal compound, carbide and a void-forming agent is deaerated under a non-oxidative atmosphere such as nitrogen gas etc. at a temperature not higher than 100° C. to displace the air with the atmospheric gas, and then heated at an elevating rate of temperature of approx. 200° C./hr to form voids in the mixture, and heated and maintained at 900° to 1150° C. for metamorphosis, and thereafter cooled at a lowering rate of temperature of approx. 200° C./hr.
• the period of metamorphosis in this case may be 3 to 6 hrs.
• condition of the heat-treatment according to the present invention is not limited to the above-mentioned one, and may vary depending on the use or non-use of the void-forming agent and on the composition of raw materials. Thus, it may be enough to heat simply at 900° to 1200° C. under a non-oxidative atmosphere, whereby metamorphosed alkali metal titanates are obtained usually within 74 hrs.
• a specimen of 0.5 mm thickness, 2.0 cm width and 3.0 cm length was prepared from the above-mentioned elastomer, all surfaces of both ends (0.5 ⁇ 2.0 cm) of the specimen were covered with silver paste.
• Example 2 the heating under nitrogen atmosphere and the cooling were conducted in a same manner as in Example 1 to get a cylindrical sinter with dark violet color and some voids inside, the weight loss being less 30%. Both sides of the sinter were coated with silver paste, and the conductivity was measured with Digital Multimeter (made by Takeda Riken Co., Ltd., Japan) to be 10.8 ⁇ . Volume resistivity calculated by the following equation was 0.530 ⁇ cm. ##EQU2##

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• 1983
  • 1983-11-21 JP JP58220352A patent/JPS60112619A/ja active Granted
• 1984
  • 1984-11-16 GB GB08429090A patent/GB2150544B/en not_active Expired
  • 1984-11-19 DE DE19843442270 patent/DE3442270A1/de active Granted
  • 1984-11-19 US US06/672,791 patent/US4609694A/en not_active Expired - Fee Related
  • 1984-11-21 FR FR8417754A patent/FR2555153B1/fr not_active Expired

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